Comparison of mechanical, chemical, and thermal activation methods on the utilisation of recycled concrete powder from construction and demolition waste

• Published in: Journal of Building Engineering Vol. 61; p. 105295
• Main Authors: Zhang, Dongsheng, Zhang, Shuxiang, Huang, Bowen, Yang, Qiuning, Li, Jiabin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2022
• Subjects: Activation methods; Microstructure; Recycled concrete powder; Strength activity index; Activation methods; Strength activity index; Microstructure; Recycled concrete powder
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2022.105295

Recycled concrete powder (RCP) poses a considerable challenge with respect to effective utilisation of construction and demolition waste (CDW) resources due to its low activity, high water demand, and potential to cause dust pollution during storage. A suitable activation method is necessary for stimulating the potential activity of RCP and enhancing its utilisation. Therefore, the effect of mechanical, chemical, and thermal activation methods on the properties of RCP were investigated in this study. Mechanical and thermal activation were helpful for the activity of RCP due to the modification of particle size and distributions. RCP exhibits a higher content of SiO2 and a lower content of CaO as well as the main crystal phases of quartz, calcite, gismondine, and dolomite. After 400–800 °C thermal activation, dolomite is not observed while the RCP shows new active components (such as larnite, calcium silicate, and calcium oxide). The chemical activation test highlights that CaO (3%) is the most optimal, followed by CaSO4 (1%) and Na2SO4 (2%), while Ca(OH)2 (4%) has the least optimal activation effect on the strength activity index (SAI) of RCP mortar. For combined activation, Ca(OH)2 and CaSO4 with 1:1 ratio has the most optimal activation effect, and the SAI reaches 80.27%. Based on the mechanical performance, SAI, and micro-characteristics, the most feasible and effective activation method is thermal activation (800 °C), followed by chemical activation (Ca(OH)2+CaSO4), and mechanical activation (75 min). This study proposes a useful combined activation method for RCP that verifiably contributes to the application of CDW. [Display omitted] •RCP activated by mechanical, chemical, and thermal activation methods.•The effect of alkali-salt combination activation on the activity of RCP is often better than that of a single activator.•Compared with mechanical and chemical activation, mortar with thermally activated RCP show better mechanical performance.